1. Field of the Invention
The invention relates to topical delivery of bioactive agents. More particularly, the invention relates to anhydrous formulations for percutaneous absorption.
2. Summary of the Related Art
Topical administration of biologically active agents has become an important method for treating a variety of skin conditions. Carlin, Cosmetic Dermatology, February 2001, pp. 35-38 teaches topical administration of vitamin C to reduce erythema of acne rosacea. Greco, Plastic and Reconstructive Surgery 105: 464-465 (2000) suggests the use of topical vitamin C in the treatment of fine wrinkles and as a stimulant for wound healing. Norman and Nelson, Skin and Aging, February 2000, pp. 28-33 teaches topical administration of a variety of common herbs to treat various dermatologic conditions. Unfortunately, many bioactive substances are not efficiently absorbed percutaneously. To overcome this problem, scientists have utilized low pH formulations or derivatives of bioactive substances. However, low pH formulations are irritating to the skin and derivatized compounds, while they may be more efficiently absorbed, are not generally efficiently bioconverted to yield the active compound. In addition, it is frequently difficult to obtain high concentrations of active in topical formulations, and in aqueous formulations, hydrophobic actives cannot be used.
There is, therefore, a need for new formulations that allow efficient topical delivery of high concentrations of underivitized bioactive substances for percutaneous absorbtion. Ideally, such formulations should be non-irritating to the skin.